CEV question for Rocket Scientists.

[darkenfast]

I've been thinking...and that usually gets me in trouble! As I remember from waaay back, the Apollo CM weighed about 11 klbs (roughly). The SM weighed in at over 50 klb. Now, the CEV is quite a bit larger than the CM, and I would assume that even with improvements in how we build spacecraft, it's still going to weigh at least 50% more than the CM. So, if the payload capacity of the CLV is around 25 tonnes (55klbs, again roughly), the back end (Service Module?) is going to have to come in a lot lighter than the Apollo SM. Which I can see for LEO, with less requirement for fuel/oxidizer, and of course no fuel cells. But, when it comes times for the lunar mission, there's a problem. Even with more energetic fuels, how is the SM going to have enough "juice" to handle LOI (with a much bigger Lander) and TEI? The only way I can figure it, is that either the EDS or the Lander has to provide LOI services. The Lander does seem to have a lot of tankage in its Descent Stage (I realize that's a notional drawing). Or, am I just missing something?

 

[propforce]

<i>"... At this time I can not go into details as to how much the CEV weights, what the propellant is etc. ..."</i><br /><br />Ummm... LOx/ Methane ? <img src="/images/icons/laugh.gif" /> <div class="Discussion_UserSignature"> </div>

 

[krrr]

If we assume a lander mass of 30 tonnes (can't be much more, otherwise the EDS would have to be larger), then it's indeed a tight thing.<br /><br />With an Isp of 370s (Lox/Methane), LOI would consume at least 11 tonnes of propellant, and TEI about 3 tonnes. Since the CEV capsule is said to mass about 9 tonnes, there's not much margin left.<br /><br />With a lander mass of 25 tonnes, it's still 10 plus 3 tonnes.